A wide variety of particle concentrators have been provided in the prior art, the simplest of these devices possibly being a pan which gold prospectors and the like filled with water and rotated for concentrating relatively heavy particles such as gold ore.
However, substantially more complex particle separators have been developed in order to facilitate the classification and separation of large quantities of particles, for example, in the mining industry for recovering small quantities of desirable particles such as gold and other heavy metals from very large quantities of ore particles.
It is to be understood that such particle concentrators may also be employed for recovering relatively low density particles such as coal from higher density ore or rock particles.
Some of the earliest particle concentrators included pans similar to those employed by gold prospectors as noted above. For example, U.S. Pat. No. 1,132,317 issued Mar. 16, 1915 to Farmer disclosed an amalgamator including a pan suspended for oscillating and swinging movement, the pan being coated with quicksilver for concentrating and amalgamating gold and other precious metals.
U.S. Pat. No. 286,342 issued Oct. 9, 1883 to Stirk disclosed a similar device with a pan supported for rotating and shaking movement in order to separate heavy and light ore particles.
These pan devices were replaced in some instances by rotating tables having their axes substantially inclined and having riffles formed on the rotating tables. Vertical inclination of the table was sufficient so that relatively high density particles were removed through a heavy concentrate outlet centrally formed at the axis of rotation for the tables. Such devices were , for example, in U.S. Pat. No. 1,141,972 issued Jun. 8, 1915 to Muhleman and U.S. Pat. No. 1,986,778 issued Jan. 1, 1935 to Hinkley.
A similar device was disclosed for separating beans into different grades in U.S. Pat. No. 1,479,082 issued Jan. 1, 1924 to Medcalf.
U.S. Pat. No. 4,008,152 issued Feb. 15, 1977 to Kleven and disclosed a metal separating process and apparatus wherein multiple inclined tables as disclosed above were operated in rotation and in series to further facilitate recovery of heavy metals. U.S. Pat. No. 1,985,513 issued Dec. 25, 1934 to McCleery and disclosed a similar concentrator employing one rotating disc constructed and operating similarly as described in the above patent.
Among more recent developments, U.S. Pat. No. 4,538,735 issued Sep. 3, 1985 to Boom, et al. disclosed apparatus for separating solids of different shapes, the apparatus including a table having a frustoconical surface and being driven in rotation for separating round and irregularly shaped solids. U.S. Pat. No. 4,068,758 issued Jan. 17, 1978 to Abdul-Rahman disclosed a feed system for a "conoidal solids separating system" and method of separating including a device generally similar to that described for the above patent.
An ore separator apparatus for separating particles of different densities was disclosed in U.S. Pat. No. 4,522,711 issued Jun. 11, 1985 to Cleland, the apparatus including a bowl with an inner liner of spiral grooves or riffles, the bowl being tilted on its axis and driven in rotation for separating ore particles. Vertical inclination of the bowl was selected so that concentrated heavy ore particles exited through a central opening in the bowl. U.S. Pat. No. 4,389,308 issued Jun. 21, 1983 also to Cleland was cited in the above patent and included apparatus of similar construction and operation.
U.S. Pat. No. 2,484,203 issued Oct. 11, 1949 to Beck also disclosed an oscillating placer separating machine including a frustoconical pan driven in oscillating rotation by a drive bar coupled eccentrically to a drive disk and to the pan for separating ore particles. In this machine, the apex or center of the frustoconical pan extends upwardly to facilitate separation as discussed in the patent.
Finally, a number of prior art devices include concentrating tables or "shaker tables" which are subjected to vibration or oscillation with water forming over the table for classifying and recovering mineral ores and the like. For example, U.S. Pat. No. 3,269,538 issued Aug. 30, 1966 to Stephan disclosed such a concentrating table having lateral elements forming a "saw tooth" surface on the inclined table which was then subjected to longitudinal oscillation to facilitate particle separation. U.S. Pat. No. 2,091,811 issued Aug. 31, 1937 to Gilbreth disclosed another concentrating table having transverse riffles on an inclined table driven in longitudinal vibratory motion by arms eccentrically coupled to a drive shaft. U.S. Pat. No. 1,964,716 issued Jul. 3, 1934 to Ater. Ater disclosed yet another placer concentrating machine generally similar to that described in the patent noted immediately above.
Yet another concentrating table has been disclosed which is constructed and operated in a manner similar to the above while further including multiple sets of leaf springs packed in lubricant to provide a mounting for facilitating longitudinal oscillation of the concentrating table.
The various devices summarized above indicate the substantial importance of efficiently and effectively separating particles of different densities, particularly but not exclusively in the mining industry. Although the various devices summarized above were generally effective for their intended purposes, it has been found desirable to further improve the effectiveness and efficiency of such concentrators in order to more accurately classify and separate particles of different densities and, for example, to facilitate recovery of very small quantities of desirable particles such as gold and other heavy metals from large quantities of ore. As an example, it is often necessary or desirable to separate only a few ounces of high density ore or even a single ounce or much less from each ton of ore to be processed. Obviously, the efficiency of such a process can be greatly enhanced if complete recovery of the desirable particles can occur in a single operation or a substantially reduced number of operations without the need for employing a relatively large number of concentrators in series to accomplish the necessary separation or classification.
Accordingly, there has been found to remain a need for further improved particle concentrators and methods of operation for facilitating effective and efficient concentration or classification of particles in accordance with the preceding discussion.